There have been a number of attempts to modify the traditional shape of the neck of a string instrument in order to facilitate ease of playing or to improve music quality.
U.S. Pat. No. 3,091,150 to Sceusa teaches a string instrument neck having a parabolic cross-section, with its apex offset from the center of the fingerboard and disposed in one quarter of the width of the fingerboard adjacent the bass edge thereof, with the long side of the parabola extending into the remaining three quarters of the fingerboard. According to Sceusa, this design allows the palm of the hand to be more comfortably extended and make it easier for the fingers to span over the treble edge of the fingerboard while permitting the thumb to depress the bass strings.
U.S. Pat. No. 4,759,250 to Lieber teaches a string instrument neck having a central ridge on the undersurface to provide a contact surface for the player's hand during playing of the instrument.
U.S. Pat. No. 4,237,765 to Valdez teaches guitars having a neck with distinct, longitudinally spaced-apart thumb-receiving notches in the back surface of the neck.
U.S. Pat. No. 5,239,908 to Attias teaches a string instrument neck having one or move concave depressions in the neck extending longitudinally along substantially the entire length of the neck, including embodiments having straight, sloping surfaces.